Production of gamma-ferric oxide hydrate and gamma-ferric oxide



Patented July 17, 1951 PRODUCTION F HYDRATE AND GAMMA-FERRIC OXIDEGAMMA-FERRIC OXIDE John Martin, Trenton, N. 1., assignor to COIumbianCarbon Company, New-.York, N. .Y., a corporation of Delaware No Drawing.Application July 11,1947,

Serial N 0. 760,497 Claims. (01. 23 200) This invention relates to theproduction of gamma-ferric oxide hydrate and gamma-ferric oxide, and.particularly to a Commercially practicable procedure whereby the desiredproducts can be manufactured economically.

Several forms of ferric oxide hydrate and ferric oxide are known and aredistinguished as alpha, beta andlgamma, the distinction being based uponinterpretation of the X-ray diffraction patterns of these compounds. Itis known that in gamma-ferric oxide, there are two types of oxygen, onetype being bound to iron atoms only, while. each oxygen atom of theother type is linked to two iron atoms and two hydrogen atoms, whereasin the alpha form the oxygen atoms are structurally equivalent 1. 8;,equivalently arranged. Gamma-ferric oxide hydrate is. described in theliterature only as the product of laboratory experiment. Puregamma-ferric oxide hydrate and gamma-ferric oxide have not been producedcommercially, since no satisfactory methods for production in volumehave been known.

It is the object of the present invention to provide a simple andeconomical method whereby gamma-ferric oxide hydrate and gamma-ferricoxide may be produced in quantity for commercial applications.

Other objects and advantages of the invention will be apparent as it isbetter understood by reference to the following specification, in whichthe preferred procedure is described- In carrying out the invention, afairly strong solution to preferably) of ferrous chloride is preparedand heated to a temperature above 150 F., desirably between 180 and 200F. The. ferrous ion in the solution is completely precipitated by therapid addition of a solution containing substantially a stoichiometricproportion of 'an alkali or alkaline earth metal hydroxide withvcontinuous stirring. The precipitate as first formed is gelatinous, andthe resulting slurry is very thick. However, if the slurry is held at atemperature of 180200 F. for 10-15 minutes, the slurry becomes quitethin. At this point, the heat is shut off and the slurry is cooledrapidly to room temperature.

Since the slurry becomes very gelatinous again upon cooling and duringsubsequent oxidation, it is desirable to dilute it substantially. Watermay be used for dilution and simultaneous cooling of the slurry. Anamount of water equal to about four times the volume of the originalslurry may be used to bring the temperature to a point under 100 F. andpreferably to about 75-85 F.

It is preferable, however, to employ for dilution and cooling a weaksolution (05-20%) of ferrous chloride in cold (about F.) water. The

amount of this solution may be equal-to about four times the volume ofthe original slurry, and

the addition of the solution should bring the tem-' perature topreferably '75-85 F.

The preferred procedure is to pour .the hot ferrous hydrate slurry intothe cooler solution. Agitation is maintained, and a strong current ofair is directed through the mixture to rapidly oxidize the precipitate.hours the precipitate will oxidized to a clean orange-yellow color..

have been. completely be dried in an oven heated to about 230 F.

In order to increase the yield, and particularly to increase the size ofthe particles as is desirable to afford products suitable for variouspurposes, the cool slurry, after oxidation, may again. be heated,preferably to -150 oxidation is continued for three and one-half to fourand one-half days. If continued for aweek, the color becomes quite dark.At the completion of the operation, the slurry may be filtered, washedand dried in an oven to about 250 F.

The productin-either case gives anX-ray diffraction patterncorresponding to that of gammaferric oxide hydrate prepared by themethod of Baudisch and Albrecht (J. Am. Chem. Soc., 54, 943, 1932)-.

The product may be dehydrated by heating to a temperature of 450-500 F.During the heating, the color will change to brown. The dehydratedproduct is gamma-ferric oxide. It is strongly ferromagnetic. It gives anX-ray diffraction pattern corresponding to gamma-ferric oxide as.obtained. by oxidation of magnetite.

The products of the procedures as herein described areespecially usefulas pigments and for other purposes for which such materials are adapted.

Various changes may be made in the procedures as described withoutdeparting from the invention or sacrificing the advantages thereof.

I claim:

1. The method of preparing gamma-ferric oxide hydrate which comprisesprecipitating the ferrous ion from a solution of ferrous chloride with asolution of a hydroxide of a metal of the class consisting of the alkaliand alkaline earth metals at a temperature between and 200 F. to form athick slurry, maintaining the temperature until the slurry is thin,diluting and rapidly In approximately two It may. then be filtered. andwashed, and the pulp may Fr Scrap iron is then added to the slurry, andaeration is continued. Fresh scrap iron should. be. added at least once.in twenty-four hours. The

3 cooling the slurry to room temperature, and oxidizing it at roomtemperature until the product has a clean orange-yellow color. 1

2. The method of preparing gamma-ferric oxide hydrate which comprisesprecipitating the ferrous ion from a solution of ferrous chloride with asolution of a hydroxide of a metal of the class consisting of the alkaliand alkaline earth metals at a temperature between 150 and 200 F. toform a thick slurry, maintaining the temperature until the slurry isthin, diluting and rapidly cooling the slurry to room temperature,oxidizing it at room temperature until the product has a cleanorange-yellow color, and filtering, washing and drying the product.

3. The method of preparing gamma-ferric oxide which comprises heatingthe product of the method as described in claim 2 to a temperaturebetween 450 and 500 F.

4. The method of preparing gamma-ferric oxide hydrate which comprisesprecipitating the ferrous ion from a solution of ferrous chloride with asolution of a hydroxide of a metal of the class consisting of the alkaliand alkaline earth metals at a temperature between 150 and 200 F. toform a thick slurry, maintaining the temperature until the slurry isthin, diluting and rapidly cooling the slurry to room temperature byadding about 4 volumes of a solution of ferrous chloride in water, andoxidizing it at room temperature until the product has a cleanorange-yellow color.

5. The method of preparing gamma-ferric oxide which comprises heatingthe product of the method as described in claim'4 to a temperaturebetween 450 and 500 F.

6. The method of preparing gamma-ferric oxide hydrate which comprisesprecipitating the ferrous ion from a solution of ferrous chloride with asolution of a hydroxide of a metal of the class consisting of the alkaliand alkaline earth metals at a temperature between 150 and 200 F. toform a thick slurry, maintaining the temperature until the slurry isthin, diluting and rapidly cooling the slurry to room temperature, andoxidizing it at room temperature with a current of air until the producthas a clean orange-yellow color.

7. The method of preparing gamma-ferric oxide hydrate which comprisesprecipitating the ferrous ion from a solution of ferrous chloride with asolution of a hydroxide of a class consisting of the alkali and alkalineearth metals at a temperature between 150 and 200 F. to form a thickslurry, maintaining the temperature until the slurry is thin, dilutingand rapidly cooling the slurry to room temperature, oxidizing it at roomtemperature until the product has a clean orange-yellow color,increasing the temperatureto 135 to 150 F., adding metallic iron andcontinuing the oxidation at the higher temperature.

8. The method of preparing gamma-ferric oxide metal of the I ture untilthe slurry is thin, diluting and rapidly cooling the slurry to roomtemperature, oxidizing it at room temperature until the product has aclean orange-yellow color, increasing the temperature to to F., addingmetallic iron, continuing the oxidation at the higher temperature, andfiltering, washin and drying the product.

10. The method of preparing gamma-ferric ox- I ide hydrate whichcomprises precipitating the ferrous ion from a solution of ferrouschloride with a solution of a hydroxide of a metal of the classconsisting of the alkali and alkaline earth metals at a temperaturebetween 150 and 200 F. to form a thick slurry, maintaining thetemperature until the slurry is thin, diluting and rapidly cooling theslurry to room temperature by adding about 4 volumes of a solution offerrous chloride in water, oxidizing it at room temperature until theproduct has a clean orange-yellow color, increasing the temperature to135 to 150 F., adding metallic iron and continuing the oxidation at thehigher temperature.

JOHN MARTIN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,368,748 Penniman and Zoph Feb.15, 1921 1,392,926 Fireman Oct. 11, 1921 1,424,635 Fireman Aug. 1, 19221,394,749 Baudisch Jan. 17, 1933 1,894,750 Baudisch Jan. 17, 19331,923,362 Frazee Aug. 22, 1933 2,111,727 Plews Mar. 22, 1938 2,127,907Fireman Aug. 23, 1938 2,357,096 Fireman Aug. 29, 1944 2,388,659 RyanNov. 6, 1945 OTHER REFERENCES Mellor, Comprehensive Treatise onInorganic and Theoretical Chemistry, vol. 13, pages 780, 781, 881, 884.Publ. by Longmans, Green 8r Co., 1934.

Baudisch and Albrecht, J. Am. Chem. 800., vol. 54, March 1932, page 943.

Welo and Baudisch, Chemical Reviews, vol. 15, 1934, pages 45-97.

Williams and Thewlis, Trans. Faraday Soc, V01. 27, 1931,.pages 767-771.

1. THE METHOD OF PREPARING GAMMA-FERRIC OXIDE HYDRATE WHICH COMPRISESPRECIPITATING THE FERROUS ION FROM A SOLUTION OF FERROUS CHLORIDE WITH ASOLUTION OF A HYDROXIDE OF A METAL OF THE CLASS CONSISTING OF THE ALKALIAND ALKALINE EARTH METALS AT A TEMPERATURE BETWEEN 150* AND 200* F. TOFORM UNTIL THE SLURRY IS THIN, DILUTING AND RAPIDLY TURE UNTIL THESLURRY IS THIN, DILUTING AND RAPIDLY COOLING THE SLURRY TO ROOMTEMPERATURE, AND OXIDIZING IT AT ROOM TEMPERATURE UNTIL THE PRODUCT HASA CLEAN ORANGE-YELLOW COLOR.